When a 61-year-old Texas man came into an emergency room claiming he was dizzy and was found to have a blood alcohol concentration of 0.37 percent, doctors assumed he was drunk.

Despite the fact the man claimed he hadn't consumed alcohol that day, most doctors still thought he was a "closet drinker," NPR reported.

It turned out that those medical professionals were wrong: the man had "auto-brewery syndrome." His stomach contained so much yeast that he was making his own in-house brew, literally.

Before he was diagnosed with the syndrome, the patient's wife -- who was a nurse -- was so concerned with her husband's constantly drunk condition that she had him regularly tested with a Breathalyzer. He would record numbers as high as 0.33 to 0.4 percent, considerably higher than the U.S. legal driving limit of 0.08 percent.

Barbara Cordell, the dean of nursing at Panola College in Carthage, Texas, and Dr. Justin McCarthy, a gastroenterologist in Lubbock, Texas, decided to figure out what was really going on.

"He would get drunk out of the blue -- on a Sunday morning after being at church, or really, just anytime," Cordell told NPR.

After isolating the patient for 24 hours and making sure there was no alcohol or sugar available, the team continued to check his blood alcohol level. The levels were as high as 0.12 percent without any alcohol consumption.

The doctors then realized that he must have been infected with high levels Saccharomyces cerevisiae, a kind of yeast that is used in alcohol fermentation and baking. They suspected that because the patient had been put on antibiotics following surgery for a broken foot in 2004, the medications might have killed all his gut bacteria. This allowed the yeast to thrive in his body.

The Environmental Protection Agency said the organism is not considered to be a pathogen, and some people take large quantities of the yeast daily as part of a "health food" diet.

"No one takes potential danger from Saccharomyces cerevesiae seriously," Dr. Michael D. Gershon, a professor in the department of pathology and cell biology at Columbia University in New York, told CBSNews.com.

Gershon added that the yeast is so non-threatening that it is often used by researchers in studies without any additional precautions.

Interviews revealed the man ate a lot of carbohydrates. That meant each time the patient ate something with starch, the high amounts of yeast in his body turned the sugars into ethanol or ethyl alcohol, which made him drunk from the inside.

To cure his illness, the patient was placed on a low-carbohydrate diet and prescribed antifungal medication to get rid of the excess yeast.

The researchers acknowledge that this condition is extremely rare. Only a handful of cases have been reported in the last three decades, including a 13-year-old girl with short gut syndrome who would get drunk if she ate carbohydrates. Another 3-year-old with the same condition became drunk when she had a fruit drink high in carbohydrates.